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Re: [css-transforms] computed style of 'transform' property

From: L. David Baron <dbaron@dbaron.org>
Date: Tue, 25 Mar 2014 14:29:45 -0700
To: Dirk Schulze <dschulze@adobe.com>
Cc: www-style <www-style@w3.org>, public-fx <public-fx@w3.org>
Message-ID: <20140325212945.GA26872@crum.dbaron.org>
On Monday 2013-12-16 09:20 +0000, Dirk Schulze wrote:
> We discussed and decided in the past that the "computed style” of the ‘transform’ property must return the specified value [1]. This has been in the spec since the first WD.
> 
> Yet, no browser ever implemented this part of the spec. For what it’s worth, all browsers seems to return a matrix()/matrix3d() string.
> 
> Even if we had the agreement from browser implementers in the past to change the behavior, no browser ever did and users are starting to rely on a matrix as returned value.
> 
> I suggest we specify the behavior of browsers and do not return the specified value. Implementations must return a string “matrix()” with 6 numerical values on a pure 2D matrix[2] (all transform functions multiplied as in [3]) and a string "matrix3d()” with 16 numerical values otherwise.

I think you're confusing the "Computed value" field of the property
description with the getComputedStyle() method.  The "Computed
style" describes the conceptual computed value, which in turn is
what is inherited and used for other things in the CSS processing
model, such as triggering CSS transforms.  Changing this to be
matrix() would break transitions and animations of CSS transforms,
since all animations would operate on matrix() values.

The getComputedStyle() method should indeed return matrix(), but
that's not what the "Computed value:" line means.

-David

-- 
𝄞   L. David Baron                         http://dbaron.org/   𝄂
𝄢   Mozilla                          https://www.mozilla.org/   𝄂
             Before I built a wall I'd ask to know
             What I was walling in or walling out,
             And to whom I was like to give offense.
               - Robert Frost, Mending Wall (1914)

Received on Tuesday, 25 March 2014 21:30:10 UTC

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